Organic Manures 



Leather Waste. 



This is made by reducing old skins and the 

 waste made by saddlers, shoemakers, curriers, and 

 bookbinders to a fine powder. The waste is treated 

 with steam, or baked, and then ground. The value 

 of this leather waste lies theoretically in its organic 

 nitrogen, since phosphoric acid [P2O5] only exists in 

 insignificant quantities. It contains about 5-5 per 

 cent, of nitrogen, but even although reduced to a 

 fine powder this nitrogen lies in the soil an indefinite 

 time, and is practically unassimilable. It is an 

 asset which cannot be utilised, so that its manurial 

 value — as experience has shown — is insignificant. 



Unscrupulous makers of chemical manures use 

 it to adulterate their goods, but leather waste ought 

 not to be employed as manure, and manure con- 

 taining it ought not to be bought. Its presence m 

 chemical manure may be detected by means of a 

 microscope. 



Refuse of Skins. 



These waste products of the skinner's industry 

 connected with hares, rabbits, etc., come from 

 Germany, and contain many feet which, not 

 having imdergone any preparation, will make a 

 manure of very slow action. Since they contain 

 small bones the tricalcic phosphate, which is not 

 very considerable, only becomes assimilable after 



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